3D Memory Super-Pillar Alignment for Deep Etch Precision
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Solution Overview
Problem
In 3D NAND memory technology, deep pillar etching faces challenges such as bowing, tilting, and distortion due to longer process times, which complicates the formation of memory cells.
Innovation Solution
The approach involves separately etching shorter sub-deck pillars and using a photo alignment process to connect them as a single super-pillar, integrating top sub-deck etching into the process flow and incorporating a deck-to-deck transition region, thereby reducing manufacturing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deep pillar etching is performed in a single continuous process, then the pillar formation is completed in one step, but the process time increases leading to bowing, tilting, and distortion
Solution Approach 1:
The deep pillar etching process is divided into multiple separate etching steps, each creating a portion of the final pillar. Intermediate layers are deposited between etching steps to separate the etching processes, allowing each etching step to be shorter and more precise, thereby avoiding bowing and distortion while maintaining overall productivity.
2Manufacturing precision
If multiple separate etching steps are used to avoid bowing and distortion, then pillar precision is improved, but the process complexity and manufacturing steps increase
Solution Approach 1:
Multiple etching steps with intermediate layer deposition are merged into an integrated process flow where each etching step is immediately followed by intermediate layer formation. This combination creates a systematic approach that manages complexity while achieving precise pillar formation without excessive process steps.
Solution Approach 2:
Intermediate layers are deposited in advance between etching steps to prepare the structure for subsequent etching portions. This preliminary action allows each etching step to start from a prepared baseline, ensuring precision while organizing the complex multi-step process into a manageable sequence.
3Length of stationary object
If longer etching process time is used to complete deep pillars, then the etching depth is achieved, but bowing and distortion occur due to process instability
Solution Approach 1:
The long etching process is segmented into multiple shorter etching steps, each achieving a portion of the required depth. By breaking down the total etching duration, each individual step maintains stability and prevents the bowing and distortion that occur in continuous long-duration etching, while the cumulative effect achieves the required deep pillar depth.
Data Source
AI summary
An embodiment of a memory device may comprise a super-pillar formed through a plurality of sub-decks, a string of memory cells formed along the super-pillar, and respective regions of transition material disposed between respective sub-decks of the plurality of sub-decks, wherein the super-pillar comprises at least a first pillar formed through a first sub-deck of the plurality of sub-decks substantially aligned with a second pillar formed through a second sub-deck of the plurality of sub-decks. Other embodiments are disclosed and claimed.